Depending on the sector and the company, CO2 emission data may be available in a timely manner, or may not be available at all. Across a spectrum of companies, the range of information disclosed and available through corporate documents and to news reporting services can vary from thorough to partial to none. When such data is available, it can be compiled (e.g., its components can be weighted) and presented as a value that is useful in rating a company relative to its peers. U.S. Pat. No. 7,277,864, assigned to the present assignee, describes rating systems that can accommodate such extra-financial data, when present. However, improvements are needed in the art to address circumstances that are all too common in which incomplete or non-existent data provides no value for rating an entity such as a company. The present invention addresses this problem using heuristics that provide multiple models for estimating CO2 total emission and for providing, automatically, an estimated value when a reported value is not available.